手机辐射究竟能否致癌？老鼠实验仅供参考

Questions and Answers on the New Study Linking Cellphones and Cancer in Rats手机辐射究竟能否致癌？老鼠实验仅供参考

Do cellphones cause cancer? Most health authorities do not think so, but a new federal study could reignite the controversy over this issue.

手机致癌吗？大部分健康专家不这么认为，但是美国联邦政府的一项新研究可能重新引发关于这个问题的争论。

The preliminary study, released Friday, found that radiation from cellphones appears to have increased the risks that male rats developed tumors in their brains and hearts. But there are many caveats and some experts are debunking the study.

周五公布的这项初步研究发现，手机辐射似乎增加了雄鼠患上脑部和心脏肿瘤的风险。但有很多需要解释的地方，而且有些专家并不认同这项研究。

Who conducted the study? Are they credible?

谁进行了这项研究？他们可信吗？

The study is from the National Toxicology Program, an interagency group in the Department of Health and Human Services whose job it is to assess the possible risks of chemicals.

Rats lived in special chambers where they were exposed to different levels of radiation of the type emitted by cellphones for nine hours a day, every day. The exposure started before they were born and continued until they were about 2 years old.

大鼠住在特殊的房间里，每天接受九小时不同强度的辐射，辐射类型与手机辐射相同。从出生前一直持续到约2岁大。

What did they find?

他们发现了什么？

About 2 to 3 percent of the male rats exposed to the radiation developed malignant gliomas, a brain cancer, compared with none in a control group that was not exposed to radiation.

约2%至3%受到辐射的雄鼠患上了恶性胶质瘤——它是一种脑部癌症——而没有受到辐射的对照组没有此类病例。

About 5 to 7 percent of the male rats exposed to the highest level of radiation developed schwannomas in their hearts, compared with none in the control group. Schwannomas are tumors that occur in cells that line the nerves. The authors concluded the brain and heart tumors were “likely caused’’ by the radiation.

Oddly enough, the incidence of tumors in females was minimal, barely different from the control group. It is not clear why the results would vary between the sexes, which is one reason some experts are questioning the findings.

奇怪的是，雌鼠的肿瘤发病率极低，与对照组几乎没有差别。不同性别出现不同结果的原因不明，这一点也令有些专家对研究结果产生质疑。

What are other caveats?

还有什么需要我们知道的？

Even for males, the differences between particular groups of rats and the control group were not statistically significant. Another anomaly was that the rats exposed to the radiation lived longer on the whole than animals in the control group. And schwannomas can occur all over the body, not just the heart, but the study did not find increased rates in other organs.

Also it was unusual that the control group had zero tumors. In previous studies at the National Toxicology Program, an average of 2 percent of rats in control groups developed gliomas. Had that happened in this study, there would have been virtually no difference between the exposed rats and the controls.

“I am unable to accept the authors’ conclusions,” said one reviewer of the study, Dr. Michael S. Lauer, deputy director for extramural research at the National Institutes of Health. Dr. Lauer, whose comments were in an appendix to the report, said it was likely that the findings represented false positives.

The amounts of radiation that rats were exposed to might be higher than what cellphone users typically experience, though toxicology studies often use higher doses to make sure to detect any effect that might exist.

这些大鼠受到的辐射强度可能高于手机用户通常受到的辐射，不过毒物学研究一般都是使用更高剂量，以确保检测到任何可能存在的影响。

So we can just dismiss this study and go on using our phones?

所以，我们可以不理会这项研究，继续使用手机吗？

Not totally. As the authors of the report write: “Given the extremely large number of people who use wireless communication devices, even a very small increase in the incidence of disease resulting from exposure to the RFR generated by those devices would have broad implications for public health.” RFR refers to radio-frequency radiation.

Dr. Otis Brawley, chief medical officer of the American Cancer Society, issued a statement on Friday that called this study “good science,” and called for further research because the animal research used very high signal strengths.

But he said, “The NTP report linking radiofrequency radiation (RFR) to two types of cancer marks a paradigm shift in our understanding of radiation and cancer risk.”

但是他说，“国家毒物管理局的报告将射频辐射与两种癌症联系起来，标志着我们在理解辐射和癌症风险方面出现思考模式的转变。”

Dr. David O. Carpenter, director of the Institute for Health and Environment at the University at Albany, said he thought the study provided backing for the human epidemiological studies that suggested cellphone use was associated with an increased risk of gliomas and acoustic neuromas, a type of schwannoma. “I think this is real,’’ he said, suggesting people used wired earpieces to talk on cellphones.

Dr. Carpenter’s view is not the prevailing one. Many studies have been conducted, including some very large ones like the Million Women Study in Britain, and a Danish study of more than 350,000 cellphone users. There also were studies examining the effects of these radio waves in animals and cells growing in petri dishes. The results are reassuring. There is no convincing evidence of any link between cellphone use and cancer or any other disease.

Also, the incidence of brain cancer in the United States has remained steady since 1992, despite the stark increase in cellphone use.

另外，从1992年至今，美国的脑部癌症发病率始终很稳定，尽管这期间手机使用量急剧上升。

The International Agency for Research on Cancer, part of the World Health Organization, rates cellphone radiation a “possible’’ human carcinogen, based on limited evidence in both people and animals. It gives the same rating to coffee and pickled vegetables.

世界卫生组织(World Health Organization)的国际癌症研究机构(International Agency for Research on Cancer)基于人和动物身上的有限证据，将手机辐射列为“可能”对人类有致癌作用的物质，与咖啡和咸菜属于同一级别。

But don’t we know that radiation causes cancer?

但是，难道我们不知道辐射致癌吗？

Ionizing radiation, the powerful type from nuclear weapons, nuclear power plants and X-ray machines, is strong enough to knock electrons off atoms and damage DNA. That can cause cancer. But the radiation from cellphones, called radio-frequency radiation, is nonionizing and not known to damage DNA.